Lapis lazuli has been studied in great detail by geologists and mineralogists due to the intense complexity of its composition. Its abundance of chemical elements is structured in at least fourteen different minerals. Each piece of extracted lapis will have a slight variation in its composition, which influences the color of the stone.
The physical properties of any stone are more susceptive to environmental changes when they are composed of a large number of minerals. Because lapis lazuli is so sophisticated in its formation, it truly has to be under exact environmental conditions – altitude, air quality, temperature – in order to exist. This is why it is such a rare gemstone!
Chilean lapis lazuli, differing from that of other deposits due to its unique location, is azure and vibrant with a uniform, granular structure that gives it a silky shine. Even among Chilean lapis there are different tones, ranging from sky blue to a nocturnal deep blue. These are products of slight variations in the stone’s mineral composition.
Daytime Sky Blue
Lighter pieces of lapis lazuli have thick white and grey veins or spots (dioxide and calcite), contrasting against the bright blue. Normally, lapis lazuli will be made of about 30% calcite, but this mineral is more abundant in lighter gems. This unique design gives one the image of a blue sky with scattered clouds. Despite its beauty, this type of lapis is seen as of a lower purity and is less valuable. It is often used in the decoration or manufacture of ornaments with large surfaces.
A more common variety of lapis lazuli resembles an evening sky. These stones are of a slightly deeper blue coloring. Lazurite, which is responsible for the blue color, makes up at least 60-70% of these stones. They also have few white or grey spots. Instead, they have a higher abundance of crystallized pyrite, which adds a glitter of tiny, golden specks. These pieces are often valued the most for their homogenous coloring and higher purity and are often used in high-quality jewelry and ornamental pieces.
Sometimes lapis stones can be such a dark blue color that they nearly look black. In these deep blue pieces, the pyrite stands out even more. The contrast of the shiny gold on the dark blue backdrop calls to mind a starry night sky. Occasionally, calcite is visible in the form of dark grey clouds. This is perhaps the rarest form of lapis lazuli and is a valuable, collectible gem.